1. Field of the Invention
The present invention relates to a coated-product with marking such as characters, numbers, figures, or patterns, a process for manufacturing the coated-product with marking; and an enclosure for an electronic apparatus utilizing the coated-product with marking.
2. Description of the Related Art
Examples of the laser marking techniques are disclosed as follows. Japanese Unexamined Patent Application Publication No. H8-132258, for example, discloses a method of forming laser-marking by irradiating a marking portion such as characters, symbols, and figures, with a laser beam, and a marking sheet utilized therefor. The method disclosed in this publication includes “irradiating to remove a prescribed portion of a colored layer in a marking sheet that includes at least a pressure-sensitive adhesive layer, a coated-sheet layer removably provided on one surface of the pressure-sensitive adhesive layer, and a laser-absorbent colored-layer provided on the other side of the pressure-sensitive adhesive layer”.
In this method, the marking portion can appear due to the contrast between the colored layer and the color of the product. Thus, the method includes a simple step of irradiating the marking sheet with a laser beam to form the marking portion without having to utilize two types of layers mutually having different colors, because the color of the outer surface of the product per se can be used for clearly displaying the marking portion ([0016] in the description).
Japanese Unexamined Patent Application Publication No. 2000-334584, for example, discloses a method of marking an appropriate position of a metallic component attached to various apparatus with various labels such as manufacturer name, model, and product number, by irradiating a marking portion such as characters, symbols, and figures, with a laser beam; and a metallic component utilized such a method. In this method, “coating is applied to unfinished surface of a component made of a metallic material, and the coated surface is irradiated with a laser beam to form predetermined engraved patterns”.
According to this method, “a desired label can simply be provided on the outer surface of the component at low cost without utilizing a nomenclature plate or original printing plate” ([0027] in the description).
Japanese Unexamined Patent Application Publication No. 2003-24868, for example, discloses a method of laser-marking by irradiating the coating of the coated-product with a laser beam to burn and remove the irradiated portion. In this method, “the coating of the coated-product is irradiated with a laser beam to burn and remove the irradiated portion, and the coating is mixed with a metallic powder as a laser beam absorbing element, which generates heat and burn the obtained coating”.
In this method, the coating of the coated-product is irradiated with a laser beam to burn and remove the irradiated portion; and excellent laser-marking can be provided on the coated-product having an arbitrary color without causing degradation of the color.
In general, a laser used for laser processing is roughly divided into two types based on oscillation wavelengths thereof.
The first type of a laser has an oscillation wavelength of approximately 1064 nm, with which markable materials may vary depending on a laser medium or laser system that amplifies a laser beam. The laser of this type having an oscillation wavelength of 1064 nm may be used for providing excellent laser processing on resin or metal parts; however, may not be used for processing transparent materials. Typical examples of this type include an Yttrium-Aluminum Garnet (Y3Al5O12:YAG) laser, YVO4 laser, and FAYb laser. A YAG laser can be used for engraving metal parts, some types of which have a short wavelength. A YVO4 laser is capable of printing marks on metal parts, and is suitable for fine laser marking. An FAYb laser has an excellent excitation efficiency.
The second type of a laser has an oscillation wavelength of approximately 10600 nm, with which letters or characters can be printed on papers or transparent materials.
A typical example of the second type includes a CO2 laser. The CO2 laser may be used for processing resin or transparent materials; however, may not be used for processing metal materials.
Materials to be laser-processed differ depending on the wavelength that a laser has, as described below. Metal materials can be processed with the laser having the oscillation wavelength of 1064 nm, because the laser beam of this type is absorbed by metal. By contrast, the metal materials may not be processed with the laser having the oscillation wavelength of 10600 nm, because the laser beam of this type is reflected by metal. However, transparent materials may not be processed with the laser having the oscillation wavelength of 1064 nm, because the laser beam of this type is easy to transmit the transparent materials. By contrast, the transparent materials can be processed with the laser having the oscillation wavelength of 10600 nm, because the laser beam of this type is absorbed by the transparent materials.
A typical example of the materials for a molding that is laser marked by the second type laser includes resin. There are natural resin and synthetic resin, each divided into thermoplastic and thermosetting types. Although resin differs in characters depending on the quality of the material; however, the resin is generally easy to process, and is comparatively light in weight but still has certain hardness. Such resin is generally transparent and colorless, so the resin is usually colored with colorant in practical use.
A typical example of the colorant for resin includes pigment. Pigment is an insoluble, either colored or colorless substance; fine particles of which are dispersed into an appropriate vehicle, and used for coloring by kneading the obtained vehicle into plastic or rubber. The pigment type colorant contains carbon (C) which can easily blacken a material without fail. The carbon-containing pigment is thus used as colorant for a material to be blackened. However, the resin per se that is mixed with the carbon-containing pigment tends to be calescent due to the carbon therein. Consequently, when the carbon-containing resin is laser-marked, the carbon in the area irradiated with laser beams may be burned.
FIG. 1 is a cross-sectional view illustrating a state where a carbon-containing coated film is burned by laser irradiation. FIG. 2 is a photographed image of a marking portion of a molding in the state illustrated in FIG. 1. In FIG. 1, a numeral 100 indicates the molding, to the surface of which a coating layer 101 is applied. An irradiated portion 102 with laser beams of the coating layer 101 has a rough surface due to burned carbon, and thus the outcome of the printed product exhibits inferior printing quality. If carbon in the large portion of the material is burned, the material color per se may change, and hence the designated color may not accurately appear in the printed product.
In response to the above-described outcome, an attempt has been made to add dye into resin as the colorant in place of pigment. The resulting resin material can be provided with laser-marking having the designated printing color without changing the original color of the material. The difference between dye and pigment is as follow; while pigment used in laser-marking contains carbon that is burned to result in changing the material in color, no carbon is contained in dye so that the color of the material remains unchanged without being burned.